High load bearing capacity nylon staple fibers with additive, and blended yarns and fabrics thereof

ABSTRACT

Nylon staple fiber with additive exhibiting a break tenacity greater than 6.5 g/den are provided as well as yarns, fabrics and other articles of manufacture produced from the fiber. Methods for producing the nylon staple fiber with additive are also provided.

This patent application claims the benefit of priority from U.S.Provisional Application Ser. No. 62/575,091 filed Oct. 20, 2017,teachings of which are herein incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The invention relates to high load bearing nylon staple fibers whichcontain an additive and methods for their production and their use inblended yams, fabrics and other articles of manufacture.

BACKGROUND OF THE INVENTION

Nylon has been manufactured and used commercially for a number of years.The first nylon fibers were of nylon 6,6, poly(hexamethylene adipamide).Nylon 6,6 fiber is still made and used commercially as the main nylonfiber. Large quantities of other nylon fibers, especially nylon 6 fiberprepared from caprolactam, are also made and used commercially. Nylonfiber is used in yarns for textile fabrics, and for other purposes. Fortextile fabrics, there are essentially two main yarn categories, namelycontinuous filament yarns and yarns made from staple fiber, i.e. cutfiber.

Nylon staple fiber has conventionally been made by melt-spinning nylonpolymer into filaments, collecting very large numbers of these filamentsinto a tow, subjecting the tow to a drawing operation and thenconverting the tow to staple fiber, e.g., in a staple cutter. The towusually contains many thousands of filaments and is generally of theorder of several hundred thousand (or more) in total denier. The drawingoperation involves conveying the tow between a set of feed rolls and aset of draw rolls (operating at a higher speed than the feed rolls) toincrease the orientation of nylon polymer in the filaments. Drawing isoften combined with an annealing operation to increase nyloncrystallinity in the tow filaments before the tow is converted intostaple fiber.

One of the advantages of nylon staple fibers is that they are readilyblended, particularly with natural fibers, such as cotton (oftenreferred to as short staple) and/or with other synthetic fibers, toachieve the advantages derivable from such blending. A particularlydesirable form of nylon staple fiber has been used for many years forblending with cotton, particularly to improve the durability andeconomics of the fabrics made from yarns comprising blends of cottonwith nylon. This is because such nylon staple fiber has a relativelyhigh load-bearing tenacity, as disclosed in Hebeler, U.S. Pat. Nos.3,044,250; 3,188,790; 3,321,448; and 3,459,845, the disclosures of whichare hereby incorporated by reference in their entirety. As explained byHebeler, the load-bearing capacity of nylon staple fiber is convenientlymeasured as the tenacity at 7% elongation (T₇), and the T₇ parameter haslong been accepted as a standard measurement and is easily read on anInstron machine.

The Hebeler process for preparing nylon staple fiber involves the nylonspinning, tow forming, drawing and converting operations hereinbeforedescribed. Improvements in the Hebeler process for preparing nylonstaple fiber have subsequently been made by modifying the nature of thetow drawing operation and by adding specific types of annealing (or hightemperature treatment) and subsequent cooling steps to the overallprocess. For example, Thompson in U.S. Pat. Nos. 5,093,195 and 5,011,645discloses nylon staple fiber preparation wherein nylon 6,6 polymer,having for example a formic acid relative viscosity (RV) of 55, is spuninto filaments which are then drawn, annealed, cooled and cut intostaple fiber having a tenacity, T, at break of about 6.8-6.9, a denierper filament of about 2.44, and a load-bearing capacity, T7, of fromabout 2.4 to 3.2. Such nylon staple fibers are further disclosed in theThompson patents as being blended with cotton and formed into yarns ofimproved yarn strength. (Both of these Thompson patents are incorporatedherein by reference in their entirety.)

Nylon staple fibers prepared in accordance with the Thompson technologyhave been blended into NYCO yarns (generally at a 50:50 nylon/cottonratio) with these yarns being used to prepare NYCO fabrics. Such NYCOfabrics, e.g., woven fabrics, find application in military combatuniforms and apparel. While such fabrics have generally provensatisfactory for military or other rugged apparel use, militaryauthorities, for example, are continually looking for improved fabricswhich may be lighter in weight, lower in cost and/or more comfortablebut still highly durable or even of improved durability.

PCT/US2015/055333 discloses high strength or load bearing nylon yarnwith break tenacity greater than 7.5 g/den and or a tenacity at 10%elongation of greater than 4.0 g/den as well as yarns, fabrics andarticles of manufacture and methods for their production.

There is desire and benefits have been shown for adding pigments such ascarbon black to a fiber particularly in military apparel. See, forexample, U.S. Pat. Nos. 5,830,572, 7,008,694 and 7,320,766.

In addition, denim and canvas fabrics, in particular dark denim, andespecially black denim, have become popular in the marketplace but areknown in the industry to have fading or colorfastness issues. Forexample, in the case of black denim, the coloration quickly fades afterrepeated launderings/wear. It is also known that the addition of nylonas a blend with cotton or cellulosic fibers significantly improves theyarn and resulting fabric's durability by improving abrasion resistance.The black dyes used to dye the black denim fabric only stain the nylonand are not as dark or permanent on the nylon fiber as they are on thecotton fiber.

However, any blending of nylon staple with a cotton or cellulosic fiberrequires high strength/high modulus.

Addition of additives such as pigments into a polymer prior to meltspinning of fibers has historically reduced fiber physical properties.For example, organic pigments tend to cross-link nylon, change itsviscosity, form spherulites which weaken fibers, and cause increaseddraw tension and filament breaks. The more pigment that is added, thelarger the strength loss. These reduced fiber properties have preventedor limited blending of pigmented nylon staple with cellulosic fibers dueto resulting low yarn and low fabric strength issues.

For example, DuPont produced pigmented nylon staple in the mid to late1990's for use in automotive upholstery. The resulting nylon stapleproduct had break tenacity under 5.5 grams/denier. The only end useidentified at that time was for the yams to be spun in 100% form forauto/home upholstery.

U.S. Pat. No. 5,290,850 discloses an improved process for melt spinninga pigmented hexamethylene adipamide fiber from a melt blend of a polymerand a colored pigment wherein the polymer is a random interpolyamide orblock polymer having two different difunctional recurring amide-formingmoieties other than those which form hexamethylene which exhibittenacities greater than 7.5 grams per denier.

There is need for additional high load bearing nylon staple fibers withadditives for use in fabrics and other articles of manufacture.

SUMMARY OF THE INVENTION

Usually, adding any inorganic or organic pigment or additive to thepolymer during the melt spinning process reduces the resulting fiberstrength. The fiber strength loss translates into lower yarn andresulting fabric strength. The inventors herein have unexpectedly foundthat adding an additive into nylon polymer prior to fiber formation anddrawing the fibers under a steam assist/annealing process results in theproduction of high strength/high modulus fibers that contain theadditive.

Accordingly, an aspect of the present invention relates to nylon staplefiber comprising nylon polymer and an additive. The nylon staple fiberwith additive of the present invention exhibits a break tenacity greaterthan 6.5 g/den. In one nonlimiting embodiment, the nylon staple fiberexhibits a tenacity at 10% elongation of greater than 3.0 g/den.Nonlimiting examples of additives which can be included in these fibersare pigments as well as additives included for fire or flame (FR)resistance and/or ultraviolet (UV) protection.

Another aspect of the present invention relates to yarn spun from thenylon staple fiber. In one nonlimiting, the yarn further comprises atleast one companion staple fiber. In one nonlimiting embodiment, thenylon content of the yarn is greater than 5%. In one nonlimitingembodiment, the nylon content of the yarn is greater than 30%. In onenonlimiting embodiment, the nylon content of the yarn is greater than50%. Such yarns can be made into fabrics and other articles ofmanufacture which are advantageously lightweight, comfortable, lowercost, and durable and hence especially suitable for use in or as, forexample, military apparel such as combat uniforms or other rugged useapparel.

Another aspect of the present invention relates to articles ofmanufacture, at least a portion of which comprises nylon staple fiber oryarn of the present invention.

In one nonlimiting embodiment, the article of manufacture is fabric.

In one nonlimiting embodiment, the fabric is dyed a solid color and/orexhibits a uniform dark shade.

In one nonlimiting embodiment, the fabric exhibits improved UV lightfastness over the closest comparison fabrics lacking suchpigment-containing or additive-containing components.

In one nonlimiting embodiment, the fabric exhibits improved dye washfastness over the closest comparison fabrics lacking suchpigment-containing or additive-containing components.

In one nonlimiting embodiment, the fabric, is a camouflage print. Thisfabric is typically constructed by use of pigmented synthetic fiber suchas polyamide 6,6 or nylon 6,6, though the fabric can also be greige, ornon-pigmented fabric. Where the fiber is pigmented, however, printingcan still occur over top of the pigmented fabric.

In one nonlimiting embodiment, the fabric exhibits a NIR (Near Infrared)reflectance in the range of 600-900 nm and/or a lower and flattened SWIR(Short Wave Infrared) reflectance in the range of 900-2500 nm Further,the fabric increases infrared (IR) reflectance curve separation betweenindividual colors used in printed fabrics in the SWIR spectrum, andprovides further disruption and improved camouflage effectivenessagainst night vision goggle surveillance.

In one nonlimiting embodiment, the fabric has improved flame resistantcharacteristics.

In one nonlimiting embodiment, the fabric exhibits an improved electricarc rating over the closest comparison fabrics lacking suchpigment-containing or additive-containing components

In one nonlimiting embodiment, the article of manufacture is denimfabric. In one nonlimiting embodiment, the denim fabric is overdyed in acolor similar to the pigment contained in the nylon staple fiber.Further, when the fiber is black, and the fabric is printed to a darkcolor, a more uniformly dyed product is obtained, because the blackfiber will act to minimize or eliminate the appearance of white fibershowing through the fabric.

In another nonlimiting embodiment, the article of manufacture is anon-woven fabric composite. End uses for such composites include, butare not limited to, industrial (felts/backings/filtration/insulation),apparel (inclusive of liner fabrics), footwear, bag/pack hard gear,durable and semi-durable (disposable or semi disposable) clothing orPPE, including FR (chemically treated or in combination with inherent FRfiber technologies), bio chemical, or other specialty protective wear.

Yet another aspect of the present invention relates to a method forproducing high strength or load bearing pigmented nylon staple fiber.The method of the present invention comprises melt-spinning nylonpolymer with pigment into filaments, then uniformly quenching thefilaments and forming a tow from a multiplicity of these quenchedfilaments. The tow is then subjected to drawing in the presence ofsteam. The drawn tow is then annealed and the resulting drawn andannealed tow is converted into staple fibers. In one nonlimitingembodiment, the annealing is performed under tension. Nylon staple fiberproduced in accordance with this method has a break tenacity greaterthan 6.5 g/den. In one nonlimiting embodiment, nylon staple fiberprepared in accordance with this method has a tenacity at 10% elongationof greater than 3.0 g/den.

DETAILED DESCRIPTION OF THE INVENTION

Provided by this disclosure are high strength or load bearing nylonstaple fiber with additive exhibiting a break tenacity greater than 6.5g/den and/or a tenacity at 10% elongation of greater than 3.0 g/den,yarns, fabrics and other articles of manufacture, at least a portion ofwhich are prepared from these fibers, and methods for their production.

Nonlimiting examples of additives included in the nylon staple fiber arepigments, additives which provide UV protection, and additives for FRresistance.

In one nonlimiting embodiment, the additive is a pigment present in anamount from about 10 parts per million to about 50,000 parts permillion. In one nonlimiting embodiment, the pigment is carbon black.Further examples of suitable pigments are: ultramarine violet, asilicate of sodium and aluminum containing sulfur; han purple,BaCuSi₂O₆; cobalt violet, cobaltous orthophosphate; manganese violet,NH₄MnP₂O₇; ultramarine, Na₈₋₁₀Al₆Si₆O₂₄S₂₋₄; Persian blue, (Na,Ca)₈(AlSiO₄)₆(S,SO₄,Cl)₁₋₂; cobalt blue, cobalt(II) stannate; Egyptianblue, (CaCuSi₄O₁₀); han blue, BaCuSi₄O₁₀; azurite, (Cu₃(CO₃)₂(OH₂));Prussian blue, ferric hexacyanoferrate; YInMn blue, (YIn_(1-x)Mn_(x)O₃);cadmium green, a mixture of CdS and Cr₂O₃; chrome green, chromic oxide;Viridian, hydrated chromic oxide; Rimnan's green, CoZnO₂; malachite,(Cu₂CO₃(OH)₂); Paris green, Cu(C₂H₂O₂)_(2.3)Cu(AsO₂)₂); Scheele's green,CuHAsO₃; Verdigris, which is typically cupric acetate and/or malachite;Verona green, (K[Al,Fe^(III)),(Fe^(II),Mg](AlSi₃,Si₄)O₁₀(OH)₂);orpiment, (As₂S₃); primrose yellow, (BiVO₄); cadmium yellow, CdS; chromeyellow, PbCrO₄; cobalt yellow, (K₃Co(NO₂)₆); yellow ochre, (Fe₂O₃.H₂O);titanium yellow; mosaic gold, SnS₂; cadmium orange, cadmiumsulfoselenide; chrome orange, (PbCrO₄+PbO); realgar, As₄S₄; cadmium red,CdSe; Indian Red; red ochre, Fe₂O₃; burnt sienna; vermillion, HgS; rawumber, Fe₂O₃+MnO₂+nH₂O+Si+AlO₃; raw sienna; ivory black; vine black;lamp black; mars black, Fe₃O₄; manganese dioxide; titanium black, Ti₂O₃;antimony white, Sb₂O₃; barium sulfate; lithopone, BaSO₄.ZnS; Cremnitzwhite, ((PbCO₃)₂·Pb(OH)₂); titanium dioxide, TiO₂; and zinc oxide, ZnO.

Also provided by this disclosure are non-woven fabric compositescomprising high tenacity fiber and cellulosic or recycled synthetic ornatural fiber.

As used herein, the terms “durable” and “durability” refer to thepropensity of a fabric so characterized to have suitably high grab andtear strength as well as resistance to abrasion for the intended end useof such fabric, and to retain such desirable properties for anappropriate length of time after fabric use has begun.

As used herein, the term “blend” or “blended”, in referring to a spunyarn, means a mixture of fibers of at least two types, wherein themixture is formed in such a way that the individual fibers of each typeof fiber are substantially completely intermixed with individual fibersof the other types to provide a substantially homogeneous mixture offibers, having sufficient entanglement to maintain its integrity infurther processing and use.

As used herein, cotton count refers to the yarn numbering system basedon a length of 840 yards, and wherein the count of the yarn is equal tothe number of 840-yard skeins required to weigh 1 pound.

All numerical values recited herein are understood to be modified by theterm “about”.

Some embodiments are based on the preparation of improved nylon staplefibers with additive having certain specified characteristics and on thesubsequent preparation of yarns, and fabrics woven from such yarns,wherein these improved nylon staple fibers with additive are blendedwith at least one other fiber. The other fibers may include cellulosicssuch as cotton, modified cellulosics such as fire-resistant (FR) treatedcellulose, polyester, rayon, animal fibers such as wool, FR polyester,FR nylon, FR rayon, m-aramid, p-aramid, modacrylic, novoloid, melamine,polyvinyl chloride, antistatic fiber, PBO (1,4-benzenedicarboxylic acid,polymer with 4,6-diamino-1,3-benzenediol dihydrochloride), PBI(polybenzimidazole), and combinations thereof. The nylon staple fibersof some embodiments can provide an increase in strength and/or abrasionresistance to yarns and fabrics. This is especially true for combinationwith relatively weaker fibers such as cotton and wool.

The specific characteristics of the nylon staple fibers with additiveprepared and used herein include fiber denier, fiber tenacity and fiberload-bearing capacity defined in terms of fiber tenacity at 7% and 10%elongation.

Realization of the desired nylon staple fiber with additive materialherein is based on the use in staple fiber manufacture of nylonpolymeric filaments and tows having certain selected properties andprocessed using certain selected processing operations and conditions.Specifically, the inventors herein have found that introduction of steambetween the feed and draw module and/or tension during annealing duringproduction of the nylon staple fiber with additive significantlyinhibits or prevents reduction in strength associated with addition ofsuch fiber additives. In one nonlimiting embodiment of the presentinvention, steam is introduced into the process by addition of a steamchamber between the feed and draw modules as this allows the excesswater to be removed prior to annealing. Without being limited to anyparticular theory, it is believed that the steam chamber adds enoughheat/steam to reduce the draw force of the nylon and help localize thedraw to the steam chamber and not over or at the feed roll exit. Steamcan be controlled by pressure.

The nylon polymer itself which is used for the spinning of nylonfilaments of the present invention can be produced in conventionalmanner. Nylon polymer suitable for use in the process and filaments ofsome embodiments comprises synthetic melt spinnable or melt spunpolymer. Such nylon polymers can include polyamide homopolymers,copolymers, and mixtures thereof which are predominantly aliphatic,i.e., less than 85% of the amide-linkages of the polymer are attached totwo aromatic rings. Widely-used polyamide polymers such aspoly(hexamethylene adipamide) which is nylon 6,6 and poly(ε-caproamide)which is nylon 6 and their copolymers and mixtures thereof can be usedin accordance with some embodiments. Other polyamide polymers which maybe advantageously used are nylon 12, nylon 4,6, nylon 6,10, nylon 6,12,nylon 12,12, and their copolymers and mixtures thereof. Illustrative ofpolyamides and copolyamides which can be employed in the process,fibers, yarns and fabrics of some embodiments are those described inU.S. Pat. Nos. 5,077,124, 5,106,946, and 5,139,729 (each to Cofer etal.) and the polyamide polymer mixtures disclosed by Gutmann in ChemicalFibers International, pages 418-420, Volume 46, December 1996. Thesepublications are all incorporated herein by reference.

In one nonlimiting embodiment, the polymer may further comprise amonomeric salt of sulfonated isopthalate (SIPA) or a monomericmethylpentamethyldiamine (MPMD). In one nonlimiting embodiment, themonomer is added at an amount of about 0.04 to about 4 wt. % of thenylon polymer.

Nylon polymer used in the preparation of nylon staple fibers hasconventionally been prepared by reacting appropriate monomers,catalysts, antioxidants and other additives, including, but not limitedto, plasticizers, delustrants, pigments, dyes, light stabilizers, heatstabilizers, antistatic agents for reducing static, additives formodifying dye ability, agents for modifying surface tension, etc.Polymerization has typically been carried out in a continuouspolymerizer or batch autoclave. The molten polymer produced thereby hasthen typically been introduced to a spin pack wherein it is forcedthrough a suitable spinneret and formed into filaments which arequenched and then formed into tows for ultimate processing into nylonstaple fiber. As used herein, spin pack is comprised of a pack lid atthe top of the pack, a spinneret plate at the bottom of the pack and apolymer filter holder sandwiched between the former two components. Thefilter holder has a central recess therein. The lid and the recess inthe filter holder cooperate to define an enclosed pocket in which apolymer filter medium, such as sand, is received. There are providedchannels interior to the pack to allow the flow of molten polymer,supplied by a pump or extruder to travel through the pack and ultimatelythrough the spinneret plate. The spinneret plate has an array of small,precision bores extending therethrough which convey, the polymer to thelower surface of the pack. The mouths of the bores form an array oforifices on the lower surface of the spinneret plate, which surfacedefines the top of the quench zone. The polymer exiting these orificesis in the form of filaments which are then directed downwards throughthe quench zone.

The extent of polymerization carried out in the continuous polymerizeror batch autoclave can generally be quantified by means of a parameterknown as relative viscosity or RV. RV is the ratio of the viscosity of asolution of nylon polymer in a formic acid solvent to the viscosity ofthe formic acid solvent itself. RV is taken as an indirect indication ofnylon polymer molecular weight. For purposes herein, increasing nylonpolymer RV is considered synonymous with increasing nylon polymermolecular weight.

As nylon molecular weight increases, its processing becomes moredifficult due to the increasing viscosity of the nylon polymer.Accordingly, continuous polymerizers or batch autoclaves are typicallyoperated to provide nylon polymer for eventual processing into staplefiber wherein the nylon polymer has an RV value of about 60 or less.

It is known that for some purposes, provision of nylon polymer ofgreater molecular weight, i.e., nylon polymer having RV values ofgreater than 70-75 and up to 140 or even 190 and higher can beadvantageous. It is known, for example, that high RV nylon polymer ofthis type has improved resistance to flex abrasion and chemicaldegradation. Accordingly, such high RV nylon polymer is especiallysuitable for spinning into nylon staple fiber which can advantageouslybe used for the preparation of papermaking felts. Procedures andapparatus for making high RV nylon polymer and staple fiber therefromare disclosed in U.S. Pat. No. 5,236,652 to Kidder and in U.S. Pat. Nos.6,235,390; 6,605,694; 6,627,129 and 6,814,939 to Schwinn and West. Allof these patents are incorporated herein by reference in their entirety.

In accordance with some embodiments, it has been discovered that staplefibers prepared from nylon polymer having an RV value which is generallyconsistent with, or in some cases higher than, that generally obtainedvia polymerization in a continuous polymerizer or batch autoclave, whenprocessed with an additive and in accordance with the spinning,quenching, feeding and drawing in the presence of steam and annealingprocedures described herein, unexpectedly exhibit increased fiber breaktenacity and increased tenacity and 10% elongation as compared tostandard product or previously described improvements. When such nylonstaple fibers with additive of improved tenacity are blended with one ormore other fibers such as cotton staple fibers, textile yarns ofimproved strength as well as lower weight can be realized. Fabrics suchas NYCO fabrics woven from such yarns exhibit the advantageshereinbefore described with respect to durability, optional lighterweight, improved comfort and/or potential lower cost as well as thebenefit of the selected additive color, UV protection or FR resistance.

In accordance with the staple fiber preparation process herein, nylonpolymer with additive, which is melt spun into tow-forming filamentsthrough one or more spin pack spinnerets and quenched, will have an RVvalue ranging from 45 to 100, including from 55 to 100, from 46 to 65,from 50 to 60, and from 65 to 100. Nylon polymer of such RVcharacteristics can be prepared, for example, using a melt blending ofpolyamide concentrate procedure such as the process disclosed in theaforementioned Kidder '652 patent. Kidder discloses certain embodimentsin which a catalyst is added for the purpose of increasing the formicacid relative viscosity (RV). Higher RV nylon polymer available formelting and spinning, such as nylon having an RV of from 65 to 100, canalso be provided by means of a solid phase polymerization (SPP) stepwherein nylon polymer flakes or granules are conditioned to increase RVto the desired extent. Such solid phase polymerization (SPP) proceduresare well-known and disclosed in greater detail in the aforementionedSchwinn/West '390, '694, '129 and '939 patents.

The nylon polymer material with additive having the requisite RVcharacteristics as specified herein is fed to a spin pack, for examplevia a twin screw melter device. In one nonlimiting embodiment, avolumetric or gravimetric feeder is used for addition of the additive.In the spin pack the nylon polymer with additive is spun by extrusionthrough one or more spinnerets into a multiplicity of filaments. Forpurposes herein, the term “filament” is defined as a relativelyflexible, macroscopically homogeneous body having a high ratio of lengthto width across its cross-sectional area perpendicular to its length.The filament cross section can be any shape, but is typically circular.Herein, the term “fiber” can also be used interchangeably with the term“filament”.

Each individual spinneret position may contain from 100 to 1950filaments in an area as small as 9 inches by 7 inches (22.9 cm×17.8 cm).Spin pack machines may contain from one to 96 positions, each of whichprovides bundles of filaments which eventually get combined into asingle tow band for drawing/downstream processing with other tow bands.

After exiting the spinnerets, the molten filaments which have beenextruded through each spinneret are typically passed through a quenchzone wherein a variety of quenching conditions and configurations can beused to solidify the molten polymer filaments with additive and renderthem suitable for collection together into tows. Quenching is mostcommonly carried out by passing a cooling gas, e.g., air, toward, onto,with, around and through the bundles of filaments being extruded intothe quenching zone from each spinneret position within the spin pack.

One suitable quenching configuration is cross-flow quenching wherein acooling gas such as air is forced into the quenching zone in a directionwhich is substantially perpendicular to the direction that the extrudedfilaments are travelling through the quench zone. Cross-flow quenchingarrangements are described, among other quenching configurations, inU.S. Pat. Nos. 3,022,539; 3,070,839; 3,336,634; 5,824,248; 6,090,485,6,881,047 and 6,926,854, teachings of which are incorporated herein byreference in their entirety.

In one nonlimiting embodiment of the staple fiber preparation processherein, the extruded nylon filaments with additive used to eventuallyform the desired nylon staple fibers with additive are spun, quenchedand formed into tows with both positional uniformity and uniformity ofquenching conditions such as described in published U.S. PatentApplication Nos. 2011/0177737 and 2011/0177738, teachings of which areherein incorporated by reference in their entirety.

Quenched spun filaments can then be combined into one or more tows. Suchtows formed from filaments from one or more spinnerets are thensubjected to a two stage continuous operation wherein the tows are drawnand annealed in the presence of steam.

Drawing of the tows is generally carried out primarily in an initial orfirst drawing stage or zone wherein bands of tows are passed between aset of feed rolls and a set of draw rolls (operating at a higher speed)to increase the crystalline orientation of the filaments in the tow. Theextent to which tows are drawn can be quantified by specifying a drawratio which is the ratio of the higher peripheral speed of the drawrolls to the lower peripheral speed of the feed rolls. The effectivedraw ratio is calculated by multiplying the 1^(st) draw ratio and the2^(nd) draw ratio.

The first drawing stage or zone may include several sets of feed anddraw rolls as well as other tow guiding and tensioning rolls such assnubbing pins. Draw roll surfaces may be made of metal, e.g., chrome, orceramic. Ceramic draw roll surfaces have been found to be particularlyadvantageous in permitting use of the relatively higher draw ratiosspecified for use in connection with the staple fiber preparationprocess herein. Ceramic rolls improve roll life as well as provide asurface that is less prone to wrap. An article appearing theInternational Fiber Journal (International Fiber Journal, 17, 1,February 2002: “Textile and Bearing Technology for Separator Rolls”,Zeitz and el.) as well as U.S. Pat. No. 4,794,680, incorporated hereinby reference, also disclose the use of ceramic rolls in to improve rolllife and reduce fiber adherence to roll surface.

While the greatest extent of drawing of the tows of filaments hereintakes place in the initial or first drawing stage or zone, someadditional drawing of the tows will generally also take place in asecond or annealing and drawing stage or zone hereinafter described. Thetotal amount of draw to which the filament tows herein are subjected canbe quantified by specifying a total effective draw ratio which takesinto account drawing that occurs in both a first initial drawing stageor zone and in a second zone or stage where annealing and someadditional drawing are conducted simultaneously.

In the process of some embodiments, the tows of nylon filaments withadditive are subjected to a total effective draw ratio of from 2.3 to5.0, including from 3.0 to 4.0. In one embodiment wherein the denier perfilament of the tows is generally smaller, a total effective draw ratiocan range from 3.12 to 3.40. In another embodiment, wherein the denierper filament of the tows is generally larger, the total effective drawratio can range from 3.5 to 4.0.

In the process herein, most of the drawing of the tows, as notedhereinbefore, occurs in the first or initial drawing stage or zone. Inparticular, from 85% to 97.5%, including from 92% to 97%, of the totalamount of draw imparted to the tows will take place in the first orinitial drawing stage or zone. The drawing operation in the first orinitial stage will generally be carried out at whatever temperature thefilaments have when passed from the quench zone of the melt spinningoperation. Frequently, this first stage drawing temperature will rangefrom 80° C. to 125° C.

In the present invention, steam is introduced between feeding anddrawing. In one embodiment, a steam chamber located between the feed anddraw modules is used.

From the first or initial drawing stage or zone, the partially drawntows are passed to a second annealing and drawing stage or zone whereinthe tows are simultaneously heated and further drawn. Heating of thetows to effect annealing serves to increase crystallinity of the nylonpolymer of the filaments. In this second annealing and drawing stage orzone, the filaments of the tows are subjected to an annealingtemperature of from 145° C. to 205° C., such as from 165° C. to 205° C.In one embodiment, the temperature of the tow in this annealing anddrawing stage may be achieved by contacting the tow with a steam-heatedmetal plate that is positioned between the first stage draw and thesecond stage drawing and annealing operation. In the present invention,annealing/oven drying under tension helps remove excess moisture gainedduring steam draw.

After the annealing and drawing stage of the process herein, the drawnand annealed tows are cooled to a temperature of less than 80° C., suchas less than 75° C. Throughout the drawing, annealing and coolingoperations described herein, the tows are maintained under controlledtension and accordingly are not permitted to relax.

After drawing in the presence of steam and annealing/oven drying undertension, the multifilament tows are converted into staple fiber withadditive by any conventional manner, for example, using a staple cutter.Staple fiber with additive formed from the tows will frequently range inlength from 2 to 13 cm (0.79 to 5.12 inches). For example, staple fiberswith additive may range from 2 to 12 cm (0.79 to 4.72 inches), from 2 to12.7 cm (0.79 to 5.0 inches), or from 5 to 10 cm. The staple fiber withadditive herein can optionally be crimped.

The high tenacity nylon staple fiber with additive formed in accordancewith the process herein will generally be provided as a collection offibers, e.g., as bales of fibers, having a denier per fiber of from 1.0to 3.0. When staple fibers having a denier per fiber of from 1.6 to 1.8,are to be prepared, a total effective draw ratio of from 3.12 to 3.40,such as from 3.15 to 3.30, can be used in the process herein to providestaple fibers of the requisite load-bearing capacity. When staple fibershaving a denier per fiber of from 2.5 to 3.0 or 2.3 to 2.7 are to beprepared, a total effective draw ratio of from 3.5 to 4.0, or from 3.74to 3.90, should be used in the process herein to provide staple fibersof the requisite load-bearing capacity.

Using this process and then annealing the fiber with additive at 180° C.using standard annealing rolls produced a significantly higher tenacityfiber with additive with a tenacity greater than 6.5 g/den.

In one nonlimiting embodiment of the current invention, a nylon staplefiber with additive is disclosed having a tenacity at 10% elongation ofat least 3.0 g/den.

Fiber with properties above and with the added advantage of the presentinvention of additives in the fiber such as pigments, UV protectors andFR resistors can be used at lower blend ratios or spun into yarns usingalternative spinning systems that significantly reduce fabricmanufacturing costs and still meet existing fabrics specifications. Thisfiber can be used to significantly reduce yarn spinning and finishedfabric costs by allowing the use of lower nylon blend levels and/oralternative spinning system while maintaining fabric properties.

The nylon staple fibers with additive provided herein are especiallyuseful for blending with other fibers for various types of textileapplications. Blends can be made, for example, with the nylon staplefibers of some embodiments in combination with other synthetic fiberssuch as rayon or polyester. Examples of blends of the nylon staplefibers herein include those made with natural cellulosic fibers such ascotton, flax, hemp, jute and/or ramie. Suitable methods for intimatelyblending these fibers may include: bulk, mechanical blending of thestaple fibers prior to carding; bulk mechanical blending of the staplefibers prior to and during carding; or at least two passes of draw frameblending of the staple fibers subsequent to carding and prior to yarnspinning.

In accordance with one nonlimiting embodiment, the high load-bearingcapacity nylon staple fibers with additive herein may be blended withcotton staple fibers and spun into textile yarn. Such yarns may be spunin conventional manner using commonly known short and long staplespinning methods including ring spinning, air jet or vortex spinning,open end spinning, or friction spinning. When the yarn blend includescotton, the resulting textile yarn will generally have a cotton fiber tonylon fiber weight ratio of from 10:90 to 90:10, including from 30:70 to70:30, and frequently a cotton:nylon weight ratio of 50:50. It iswell-known in the art that nominal variation of the fiber content, e.g.,52:48 is also considered to be a 50:50 blend.

The nylon/cotton (NYCO) yarns of some embodiments can be used inconventional manner to prepare NYCO woven fabrics of especiallydesirable properties for use in military or other rugged use apparel.Thus, such yarns may be woven into 2×1 or 3×1 twill NYCO fabrics. SpunNYCO yarns and 3×1 twill woven fabrics comprising such yarns are ingeneral described and exemplified in U.S. Pat. No. 4,920,000 to Green,incorporated herein by reference.

NYCO woven fabrics, of course, comprise both warp and weft (fill) yarns.The woven fabrics of some embodiments are those which have the NYCOtextile yarns herein woven in an least one, and optionally both, ofthese directions. In one embodiment, fabrics herein of especiallydesirable durability and comfort will have yarns woven in the weft(fill) direction comprising nylon staple fibers with additive herein andwill have yarns woven in the warp direction comprising nylon staplefibers with additive herein.

The woven fabrics of some embodiments made using yarns which comprisethe high load bearing nylon staple fibers with additive herein can useless of the nylon staple fibers than conventional NYCO fabrics whileretaining many of the desirable properties of such conventional NYCOfabrics. Thus, such fabrics can be made to be relatively lightweight andlow cost while still desirably durable. Alternatively, such fabrics canbe made using equal or even greater amounts of the nylon staple fiberswith additive herein in comparison with nylon fiber content ofconventional NYCO fabrics with such fabrics herein providing superiordurability properties.

In one nonlimiting embodiment, nylon staple fiber of the presentinvention with pigment additive is used to produce an article ofmanufacture such as a denim fabric. Currently, black dyed 100% cottondenim fabric has fade and wear issues after repeated launderings. Whilenon-pigmented, high strength nylon staple can be added to improve fabricdurability and strength, fading issues remain. Adding a pigmented, highstrength nylon staple of the present invention comprising an additivesuch as carbon black reduces the black color appearance loss andimproves wear life. As will be understood by the skilled artisan uponreading this disclosure, alternative pigments for colors such as blue,green and tan can also be used. In this nonlimiting embodiment,pigmented fibers with 1-5% by weight of, for example, carbon black ordenim blue coloration can be used in denim to reduce fabric fadingissues and improve durability. Incorporation of these fibers intofabrics is particularly useful in articles of manufacture which are dyeda solid color and/or wherein improved uniformity in dyeing such as indark shades is desired.

In some embodiments, the denim fabric may be overdyed in a color similarto the pigment contained in the nylon staple fiber. Camouflage printedfabrics may also be produced from the nylon staple fiber with additiveof the present invention.

Such fabrics are expected to exhibit improved dye wash fastness.

Further, the addition of carbon black into the fiber or on the fabric asa topical treatment is known to improve concealment of theuniform/wearer when viewed through night vision goggles using NearInfrared (NIR) and Short Wave Infrared (SWIR) technology.

Accordingly, in another nonlimiting embodiment, nylon staple pigmentedfibers of the present invention with carbon black in the range of 10 to1000 ppm can be used to improve concealment of articles of manufacturesuch as uniforms containing the fiber when viewed under SWIR/NIR nightvision goggles. In one nonlimiting embodiment, incorporation of apigmented nylon staple fiber of the present invention comprising aconventional dyestuff can lower the NIR reflectance in the range of600-900 nm without requiring any pre- or post-treatments or use of ametalized or special pigment formulations and without significantlychanging the shade in the visible spectrum, thus enhancing thecamouflage disruption and effectiveness against night vision gogglesurveillance.

In another nonlimiting embodiment, incorporation of a pigmented nylonstaple fiber of the present invention comprising a conventional dyestuffcan lower and flatten the Short Wave Infrared reflectance (SWIR) in therange of 900-2500 nm without requiring pre- or post-treatments or use ofmetalized or special pigment formulations required for solid color andprinted camouflage NYCO fabrics, and without significantly changing theshade in the visible spectrum thus enhancing the camouflage disruptionand effectiveness against night vision goggle surveillance. In yetanother nonlimiting embodiment, incorporation of a pigmented nylonstaple fiber of the present invention comprising a conventional dyestuffcan increase the level of separation between print colors in the SWIR inthe range of 900-2500 nm without requiring pre- or post-treatments oruse of metalized or special pigment formulations, thus enhancing thecamouflage disruption and effectiveness against night vision gogglesurveillance. Such-fabrics of the present invention are also expected toexhibit an improved electric arc rating.

In another nonlimiting embodiment, incorporation of nylon staple fiberwith an additive providing UV protection or an additive providing FRresistance into an article of manufacture such as a fabric results inimproved UV light fastness and/or flame retardance.

The present invention also relates to non-woven fabric compositescomprising high tenacity fiber of the present invention. The hightenacity fiber can be combined with various cellulosic or recycledsynthetic or natural fiber technologies. In one embodiment, the hightenacity fiber is combined with recycled denim. End uses for thenon-woven fabric composites include, but are not limited to, industrial(felts/backings/filtration/insulation), apparel (inclusive of linerfabrics), footwear, bag/pack hard gear, durable and semi-durable(disposable or semi disposable) clothing or PPE, including FR(chemically treated or in combination with inherent FR fibertechnologies), bio chemical, or other specialty protective wear.

As will be understood by the skilled artisan upon reading thisdisclosure, alternative methods and apparatus to those exemplifiedherein which result in at least a portion of the yarn on the top surfaceor at least a portion of the yarn on the bottom surface having fiberswith a permanently modified cross-section and that are melt fusedtogether are available and use thereof is encompassed by the presentinvention.

All patents, patent applications, test procedures, priority documents,articles, publications, manuals, and other documents cited herein arefully incorporated by reference to the extent such disclosure is notinconsistent with this invention and for all jurisdictions in which suchincorporation is permitted.

Test Methods and Examples

The following Test Methods and Examples demonstrate the presentinvention and its capability for use. The invention is capable of otherand different embodiments, and its several details are capable ofmodifications in various apparent respects, without departing from thescope and spirit of the present invention. Accordingly, the Test Methodsand Examples are to be regarded as illustrative in nature andnon-limiting.

Nylon Polymer Relative Viscosity

The formic acid RV of nylon materials used herein refers to the ratio ofsolution and solvent viscosities measured in a capillary viscometer at25° C. The solvent is formic acid containing 10% by weight of water. Thesolution is 8.4% by weight nylon polymer dissolved in the solvent. Thistest is based on ASTM Standard Test Method D 789. The formic acid RVsare determined on spun filaments, prior to or after drawing, and can bereferred to as spun fiber formic acid RVs.

Instron Measurements on Staple Fibers

All Instron measurements of staple fibers herein are made on singlestaple fibers, taking appropriate care with the clamping of the shortfiber, and making an average of measurements on at least 10 fibers.Generally, at least 3 sets of measurements (each for 10 fibers) areaveraged together to provide values for the parameters determined.

Filament Denier

Denier is the linear density of a filament expressed as weight in gramsof 9000 meters of filament. Denier can be measured on a Vibroscope fromTextechno of Munich, Germany. Denier times (10/9) is equal to decitex(dtex). Denier per filament can be determined gravimetrically inaccordance with ASTM Standard Test Method D 1577. A Favimat machinehaving a vibration based linear density measurement such as used in aVibroscope can also be used to determine DPF or denier per filament ofthe individual fiber and is comparable to ASTM D1577.

Tenacity at Break

Tenacity at break (T) is the maximum or breaking force of a filamentexpressed as force per unit cross-sectional area. The tenacity can bemeasured on an Instron model 1130 available from Instron of Canton,Mass, and is reported as grams per denier (grams per dtex). Filamenttenacity at break (and elongation at break) can be measured according toASTM D 885.

Filament Tenacity at 7% and 10% Elongation

Filament tenacity at 7% elongation (T7) is the force applied to afilament to achieve 7% elongation divided by filament denier. T7 can bedetermined according to ASTM D 3822. Tenacity at 10% elongation can berun on a Favimat, which is comparable to ASTM D3822.

Yarn Strength

Strength of the spun nylon/cotton yarns herein can be quantified via aLea Product value or yarn breaking tenacity. Lea Product and skeinbreaking tenacity are conventional measures of the average strength of atextile yarn and can be determined in accordance with ASTM D 1578. LeaProduct values are reported in units of pounds force. Breaking tenacityis reported in units of cN/tex.

Fabric Weight

Fabric weight or basis weight of the woven fabrics herein can bedetermined by weighing fabric samples of known area and calculatingweight or basis weight in terms of grams/m² or oz/yd² in accordance withthe procedures of the standard test method of ASTM D 3776.

Fabric Grab Strength

Fabric grab strength can be measured in accordance with ASTM D 5034.Grab strength measurements are reported in pounds-force in both warp andfill directions.

Fabric Tear Strength—Elmendorf

Fabric tear strength can be measured in accordance with ASTM D 1424titled Standard Test Method for Tearing Strength of Fabrics byFalling-Pendulum Type (Elmendorf) Apparatus. Grab strength measurementsare reported in pounds-force in both warp and fill directions.

Colorfastness to Laundering—AATCC Test Method 61

AATCC 61 is used to evaluate the colorfastness to laundering of textilesexpected to withstand frequent launderings. Test specimens are attachedto multi-fiber swatches and stainless steel balls are loaded intostainless steel canisters to replicate abrasion. The canisters are thenloaded into the machine and the 45 minute test begins. After laundering,specimens are dried, conditioned, and evaluated with both the Gray Scalefor Color Change and the Gray Scale for Staining. Dimensional changes offabrics after laundering are also tested and applied to evaluations,according to AATCC Test Method 135.

Colorfastness to Light—AATCC Test Method 16

This test method provides the general principles and procedures whichare currently in use for determining the colorfastness to light oftextile materials. The test options described are applicable to textilematerials of all kinds and for colorants, finishes and treatmentsapplied to textile materials.

Test options included are:

1—Enclosed Carbon-Arc Lamp, Continuous Light 2—Enclosed Carbon-Arc Lamp,Alternate Light and Dark 3—Xenon-Arc Lamp, Continuous Light, Black PanelOption 4—Xenon-Arc Lamp, Alternate Light and Dark 5—Xenon-Arc Lamp,Continuous Light, Black Standard Option 6—Daylight Behind GlassColorimetric Analysis

NIR and SWIR analyses are performed using any of commercially availablecolor spectrophotometric instruments such as an UltraScan Prospectrophotometer, available from HunterLab.

Example 1:

Various fibers of the present invention were tested as described herein.Results are depicts in the following Table 1.

TABLE 1 Pigment Addition T420BK Fiber Properties Tenacity at Tenacity at7% 10% Fiber Tenacity Elongation Elongation Elongation Property DPF(g/den) (%) (g/den) (g/den) 1000 ppm 1.60 7.29 53.44 1.98 3.33 carbonblack average 1.25% 1.59 7.04 45.33 1.88 3.28 Carbon Black Average

1. A nylon staple fiber comprising: a nylon polymer; and an additive,wherein the nylon staple fiber has a break tenacity greater than 6.5g/den.
 2. The nylon staple fiber of claim 1 wherein the additive isselected from a pigment, an additive for ultraviolet (UV) protection oran additive for flame or fire (FR) resistance.
 3. The nylon staple fiberof claim 1 wherein the additive is a pigment present in an amount fromabout 10 parts per million to about 50,000 parts per million.
 4. Thenylon staple fiber of claim 1 wherein the nylon polymer is selected fromthe group consisting of nylon 6,6, nylon 6, and combinations thereof. 5.The nylon staple fiber of claim 1 wherein the nylon polymer furthercomprises a monomeric salt of sulfonated isopthalate (SPA) in an amountof about 0.04 to about 4 wt % nylon polymer.
 6. The nylon staple fiberof claim 1 wherein the nylon polymer further comprises a monomericmethylpentamethyldiamine (MPMD) in an amount of about 0.04 to about 4wt. % nylon polymer.
 7. The nylon staple fiber of claim 1 wherein thetenacity at 10% elongation is greater than 3.0 g/den.
 8. A yarn spunfrom the nylon staple fiber of claim
 1. 9. The yarn of claim 8 furthercomprising at least one companion staple fiber.
 10. The yam of claim 9wherein the companion staple fiber is selected from the group consistingof cellulosics, modified cellulosics, animal fibers, fire resistantpolyester, fire resistant nylon, fire resistant rayon, fire resistanttreated cellulose, m-aramid, p-aramid, modacrylic, novoloid, melamine,polyvinyl chloride, antistatic fiber, PBO (1,4-benzenedicarboxylic acid,polymer with 4,6-diamino-1,3-benzenediol dihydrochloride) and PBI(polybenzimidazole), and combinations thereof.
 11. The yarn of claim 1wherein the nylon content is 5% or greater.
 12. An article ofmanufacture at least a portion of which comprises nylon staple fiber ofclaim
 1. 13. The article of manufacture of claim 12 which is a fabric.14. The article of manufacture of claim 12 which is a denim fabric. 15.(canceled)
 16. The article of manufacture of claim 12 which is anon-woven fabric composite. 17-26. (canceled)
 27. A method for producinghigh strength or load bearing nylon staple fiber with additive, saidmethod comprising: melt-spinning nylon polymer with additive intofilaments; uniformly quenching the filaments; forming a tow from amultiplicity of these quenched filaments; subjecting the tow to drawingin the presence of steam, annealing the drawn tow; and converting theresulting drawn and annealed tow into staple fibers.
 28. The method ofclaim 27 wherein the additive is selected from a pigment, an additivefor UV protection or an additive for FR resistance.
 29. The method ofclaim 27 wherein annealing is performed under tension.
 30. The method ofclaim 27 wherein the nylon staple fiber has a break tenacity greaterthan 6.5 g/den.
 31. The method of claim 27 wherein the nylon staplefiber has a tenacity at 10% elongation of greater than 3.0 g/den.